TLA Line data Source code
1 : //
2 : // Copyright (c) 2026 Michael Vandeberg
3 : //
4 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 : //
7 : // Official repository: https://github.com/cppalliance/corosio
8 : //
9 :
10 : #ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_TRAITS_HPP
11 : #define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_TRAITS_HPP
12 :
13 : #include <boost/corosio/detail/platform.hpp>
14 :
15 : #if BOOST_COROSIO_HAS_SELECT
16 :
17 : #include <boost/corosio/native/detail/make_err.hpp>
18 : #include <boost/corosio/native/detail/reactor/reactor_descriptor_state.hpp>
19 :
20 : #include <system_error>
21 :
22 : #include <errno.h>
23 : #include <fcntl.h>
24 : #include <netinet/in.h>
25 : #include <sys/select.h>
26 : #include <sys/socket.h>
27 : #include <unistd.h>
28 :
29 : /* select backend traits.
30 :
31 : Captures the platform-specific behavior of the portable select() backend:
32 : manual fcntl for O_NONBLOCK/FD_CLOEXEC, FD_SETSIZE validation,
33 : conditional SO_NOSIGPIPE, sendmsg(MSG_NOSIGNAL) where available,
34 : and accept()+fcntl for accepted connections.
35 : */
36 :
37 : namespace boost::corosio::detail {
38 :
39 : class select_scheduler;
40 :
41 : struct select_traits
42 : {
43 : using scheduler_type = select_scheduler;
44 : using desc_state_type = reactor_descriptor_state;
45 :
46 : static constexpr bool needs_write_notification = true;
47 :
48 : // No extra per-socket state or lifecycle hooks needed for select.
49 : struct stream_socket_hook
50 : {
51 HIT 28 : std::error_code on_set_option(
52 : int fd, int level, int optname,
53 : void const* data, std::size_t size) noexcept
54 : {
55 28 : if (::setsockopt(
56 : fd, level, optname, data,
57 28 : static_cast<socklen_t>(size)) != 0)
58 MIS 0 : return make_err(errno);
59 HIT 28 : return {};
60 : }
61 31937 : static void pre_shutdown(int) noexcept {}
62 10622 : static void pre_destroy(int) noexcept {}
63 : };
64 :
65 : struct write_policy
66 : {
67 119036 : static ssize_t write(int fd, iovec* iovecs, int count) noexcept
68 : {
69 119036 : msghdr msg{};
70 119036 : msg.msg_iov = iovecs;
71 119036 : msg.msg_iovlen = static_cast<std::size_t>(count);
72 :
73 : #ifdef MSG_NOSIGNAL
74 119036 : constexpr int send_flags = MSG_NOSIGNAL;
75 : #else
76 : constexpr int send_flags = 0;
77 : #endif
78 :
79 : ssize_t n;
80 : do
81 : {
82 119036 : n = ::sendmsg(fd, &msg, send_flags);
83 : }
84 119036 : while (n < 0 && errno == EINTR);
85 119036 : return n;
86 : }
87 : };
88 :
89 : struct accept_policy
90 : {
91 7064 : static int do_accept(
92 : int fd, sockaddr_storage& peer, socklen_t& addrlen) noexcept
93 : {
94 7064 : addrlen = sizeof(peer);
95 : int new_fd;
96 : do
97 : {
98 7064 : new_fd = ::accept(
99 : fd, reinterpret_cast<sockaddr*>(&peer), &addrlen);
100 : }
101 7064 : while (new_fd < 0 && errno == EINTR);
102 :
103 7064 : if (new_fd < 0)
104 3532 : return new_fd;
105 :
106 3532 : if (new_fd >= FD_SETSIZE)
107 : {
108 MIS 0 : ::close(new_fd);
109 0 : errno = EINVAL;
110 0 : return -1;
111 : }
112 :
113 HIT 3532 : int flags = ::fcntl(new_fd, F_GETFL, 0);
114 3532 : if (flags == -1)
115 : {
116 MIS 0 : int err = errno;
117 0 : ::close(new_fd);
118 0 : errno = err;
119 0 : return -1;
120 : }
121 :
122 HIT 3532 : if (::fcntl(new_fd, F_SETFL, flags | O_NONBLOCK) == -1)
123 : {
124 MIS 0 : int err = errno;
125 0 : ::close(new_fd);
126 0 : errno = err;
127 0 : return -1;
128 : }
129 :
130 HIT 3532 : if (::fcntl(new_fd, F_SETFD, FD_CLOEXEC) == -1)
131 : {
132 MIS 0 : int err = errno;
133 0 : ::close(new_fd);
134 0 : errno = err;
135 0 : return -1;
136 : }
137 :
138 : #ifdef SO_NOSIGPIPE
139 : // Best-effort: SO_NOSIGPIPE is a safety net; write paths
140 : // also use MSG_NOSIGNAL where available. Failure here
141 : // should not prevent the accepted connection from being used.
142 : int one = 1;
143 : (void)::setsockopt(
144 : new_fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one));
145 : #endif
146 :
147 HIT 3532 : return new_fd;
148 : }
149 : };
150 :
151 : // Create a plain socket (no atomic flags -- select is POSIX-portable).
152 3674 : static int create_socket(int family, int type, int protocol) noexcept
153 : {
154 3674 : return ::socket(family, type, protocol);
155 : }
156 :
157 : // Set O_NONBLOCK, FD_CLOEXEC; check FD_SETSIZE; optionally SO_NOSIGPIPE.
158 : // Caller is responsible for closing fd on error.
159 3674 : static std::error_code set_fd_options(int fd) noexcept
160 : {
161 3674 : int flags = ::fcntl(fd, F_GETFL, 0);
162 3674 : if (flags == -1)
163 MIS 0 : return make_err(errno);
164 HIT 3674 : if (::fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
165 MIS 0 : return make_err(errno);
166 HIT 3674 : if (::fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
167 MIS 0 : return make_err(errno);
168 :
169 HIT 3674 : if (fd >= FD_SETSIZE)
170 MIS 0 : return make_err(EMFILE);
171 :
172 : #ifdef SO_NOSIGPIPE
173 : // Best-effort: SO_NOSIGPIPE is a safety net; write paths
174 : // also use MSG_NOSIGNAL where available. Match develop's
175 : // predominant behavior of ignoring failures here rather
176 : // than failing socket creation.
177 : {
178 : int one = 1;
179 : (void)::setsockopt(
180 : fd, SOL_SOCKET, SO_NOSIGPIPE, &one, sizeof(one));
181 : }
182 : #endif
183 :
184 HIT 3674 : return {};
185 : }
186 :
187 : // Apply protocol-specific options after socket creation.
188 : // For IP sockets, sets IPV6_V6ONLY on AF_INET6 (best-effort).
189 : static std::error_code
190 3592 : configure_ip_socket(int fd, int family) noexcept
191 : {
192 3592 : if (family == AF_INET6)
193 : {
194 13 : int one = 1;
195 13 : (void)::setsockopt(
196 : fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
197 : }
198 :
199 3592 : return set_fd_options(fd);
200 : }
201 :
202 : // Apply protocol-specific options for acceptor sockets.
203 : // For IP acceptors, sets IPV6_V6ONLY=0 (dual-stack, best-effort).
204 : static std::error_code
205 62 : configure_ip_acceptor(int fd, int family) noexcept
206 : {
207 62 : if (family == AF_INET6)
208 : {
209 8 : int val = 0;
210 8 : (void)::setsockopt(
211 : fd, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
212 : }
213 :
214 62 : return set_fd_options(fd);
215 : }
216 :
217 : // Apply options for local (unix) sockets.
218 : static std::error_code
219 20 : configure_local_socket(int fd) noexcept
220 : {
221 20 : return set_fd_options(fd);
222 : }
223 :
224 : // Non-mutating validation for fds adopted via assign(). Select's
225 : // reactor cannot handle fds above FD_SETSIZE, so reject them up
226 : // front instead of letting FD_SET clobber unrelated memory.
227 : static std::error_code
228 14 : validate_assigned_fd(int fd) noexcept
229 : {
230 14 : if (fd >= FD_SETSIZE)
231 MIS 0 : return make_err(EMFILE);
232 HIT 14 : return {};
233 : }
234 : };
235 :
236 : } // namespace boost::corosio::detail
237 :
238 : #endif // BOOST_COROSIO_HAS_SELECT
239 :
240 : #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_TRAITS_HPP
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